New developments in laser technology and theoretical modeling has allowed physicists to control chemical reactions using lasers and to attain an understanding of the underlying photochemical reaction mechanism. The book gives an up-to-date presentation of this research area, covering time-resolved spectroscopy and the dynamical behavior of electronically excited states.
An introduction to the rapidly evolving methodology of electronic excited states For academic researchers, postdocs, graduate and undergraduate students, Quantum Chemistry and Dynamics of Excited States: Methods and Applications reports the most updated and accurate theoretical techniques to treat electronic excited states. From methods to deal with stationary calculations through time-dependent simulations of molecular systems, this book serves as a guide for beginners in the field and knowledge seekers alike. Taking into account the most recent theory developments and representative applications, it also covers the often-overlooked gap between theoretical and computational chemistry. An excellent reference for both researchers and students, Excited States provides essential knowledge on quantum chemistry, an in-depth overview of the latest developments, and theoretical techniques around the properties and nonadiabatic dynamics of chemical systems. Readers will learn: ● Essential theoretical techniques to describe the properties and dynamics of chemical systems ● Electronic Structure methods for stationary calculations ● Methods for electronic excited states from both a quantum chemical and time-dependent point of view ● A breakdown of the most recent developments in the past 30 years For those searching for a better understanding of excited states as they relate to chemistry, biochemistry, industrial chemistry, and beyond, Quantum Chemistry and Dynamics of Excited States provides a solid education in the necessary foundations and important theories of excited states in photochemistry and ultrafast phenomena.
Molecules are rarely found in electronic excited states under standard conditions but such states play a major role in chemical reactions. Computational prediction of properties of such states is hard with standard DFT protocols, as made evident by the failure of linear response TDDFT in predicting energies of charge-transfer excited states with semi-local functionals. Condensed phase dynamics of excited states are even more intractable on account of the computational cost scaling exponentially with the number of condensed phase particles under consideration. However, it is still possible to develop cheap but accurate approximations for properties and dynamics of excited states, and herein we describe some of the methods developed by us along those directions. We first demonstrate that restricted open shell Kohn-Sham (ROKS) calculations with semi-local hybrid functionals give good agreement with experimental absorption energies, emission energies, zero-zero transition energies and singlet-triplet gaps of CT states-unlike TDDFT, which significantly underestimates energy gaps. We then show that is possible to compute the effects of conical intersections on non-adiabatic dynamics of chemical systems by deriving perturbative memory kernels for the linear vibronic coupling model, and employing them to calculate the population dynamics of the Fe(II)-Fe(III) self-exchange reaction. Finally, we present a relationship between perturbation theory traces of the spin-boson model that allows us to obtain the exact solution with arbitrary initial harmonic bath state in the slow bath limit. We then attempt to generalize it to multiple states, and devise a similar trace relationship which makes it trivial to write down closed form expressions for populations and kernels to arbitrary order for any n level system.
Nonadiabatic transition is a highly multidisciplinary concept and phenomenon, constituting a fundamental mechanism of state and phase changes in various dynamical processes of physics, chemistry and biology, such as molecular dynamics, energy relaxation, chemical reaction, and electron and proton transfer. Control of molecular processes by laser fields is also an example of time-dependent nonadiabatic transition. In this new edition, the original chapters are updated to facilitate enhanced understanding of the concept and applications. Three new chapters OCo comprehension of nonadiabatic chemical dynamics, control of chemical dynamics, and manifestation of molecular functions OCo are also added.
In this work we have studied the properties of Rydberg states of amines and ethers with a view to their application to and importance for the chemistry of energetic materials. We have learned that in clusters these Rydberg states can be quite reactive and, in fact, they dominate the excited state chemistry and dynamics through electron transfer reactions. This unexpected and new phenomenon can be understood based on available excited state orbitals (Rydberg, sigma*, pi*) for the solvent molecules. If the solvent molecule for the amine or ether is another amine, ether, or aromatic, a low lying electron transfer state is generated, due to the exchange interaction, which is the first step in a chain of chemical reactions. We conclude that these electron transfer states generated from Rydberg state-solvent interactions are quite general and can represent the initial step in electron transfer oxidation-reduction chemistry for energetic materials.
A companion volume to Conceptual Trends in Quantum Chemistry, this work contains eight contributions focusing on important conceptual trends in atomic and molecular theory. The polarization between ab initio and semi-empirical methods is thoroughly analyzed in two of the articles, which also provide bridges between such procedures. Hydrogen-transfer theory and electron delocalization are treated in two further papers. Explicitly time-dependent descriptions of intermolecular dynamics, which constitute a characteristic trend in current research, are represented by an article about the quantum dynamics of diatoms in external fields. A view of certain atomic excited states is presented in a paper on collective and independent particle character, and a new theoretical tool is surveyed in an article on dimensional scaling. The final article analyzes density functional theory.
Exploration of the similarities and differences between the dynamics of electronically-excited states in gaseous, cluster and condensed media, focussing on the effect of the medium. The processes involved in studying the dynamics of electronically-excited states include energy transfer, chemical reaction, decomposition to neutral and ionic fragments, proton and electron transfer.
